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Sudden Oak Death may be widespread in East Bay, situation on UC Berkeley campus indicates
15 January 2002

By Robert Sanders, Media Relations

Berkeley - Sudden Oak Death, a disease injuring or killing trees up and down the Pacific Coast, has likely invaded much of the East Bay, given the recent discovery that the disease is widespread on the University of California, Berkeley, campus.

"I don't think it has been around the East Bay for a long time, but long enough to spread," said Matteo Garbelotto, a leading researcher in Sudden Oak Death and a forest pathologist at UC Berkeley's College of Natural Resources. "The Berkeley campus isn't an island, so if it's here, it's probably all around us, and we just haven't noticed it yet."


"What we discover on the UC Berkeley campus is going to advance our scientific understanding of the disease, determine the disease's host range, and hopefully come up with a way to control it."

-- Matteo Garbelotto


Last fall, Garbelotto noticed yellowed leaves on some California bay laurels and a California buckeye on the campus and, after DNA tests, confirmed the presence of Sudden Oak Death. A more complete survey of the campus in November turned up 34 infected trees and shrubs, including some at the world-renowned UC Botanical Garden.

No treatment or cure for the disease is known, but Garbelotto is at the forefront of research to understand the disease and its host range, and to find effective treatments.

"What we discover on the UC Berkeley campus is going to advance our scientific understanding of the disease, determine the disease's host range, and hopefully come up with a way to control it," said Garbelotto, who is also an adjunct professor in UC Berkeley's Department of Environmental Science, Policy & Management.

The campus has already formed an SOD Task Force and alerted the surrounding community, including the City of Berkeley and the East Bay Regional Parks, that the disease could be elsewhere in the East Bay. It's also mounted an effort to educate campus groundskeepers, gardeners, arborists and horticulturists how to recognize infected plants.

Once the campus survey confirmed Sudden Oak Death in the UC Botanical Garden, director Ellen Simms immediately instituted a quarantine on all plants and plant parts, stopping distribution to scientists and arboretums and suspending the sale of plants to the public.

"The UC Botanical Garden is a museum of living plants, one of the most diverse botanical gardens in the country," said Simms, associate professor of integrative biology at UC Berkeley. "Sudden oak death could profoundly affect the garden and its scientific mission."

Simms cautions that the disease is so new and so little is yet known about it that the ultimate impact on the garden is impossible to predict. The garden now has an important scientific role to play in clarifying the host range of the microbe responsible for the disease.

"Not only does the pathogen infect an alarming number of species, its hosts are taxonomically diverse, currently comprising 12 plant families," Simms said. "This broad taxonomic diversity suggests that the actual host range is likely to be much larger. With its enormous taxonomic diversity exposed to the pathogen at a relatively early stage in the epidemic, the UC Botanical Garden will now play a significant role in documenting the list of hosts."

While some hosts are very efficient at transmitting the pathogen, others appear unable to do so. Research at the UC Botanical Garden can determine which hosts are poor transmitters of the disease, and that will help limit the number of plants destroyed in eradication efforts, such as one underway in Oregon.

Also, because the garden holds plants from many habitats and continents, research there could rapidly assess the world-wide taxonomic diversity of hosts and put the garden in a position to provide Web-accessible tools for identifying infections on these hosts.

"With this information, homeowners and other gardeners would be able to identify infected plants, and those living in infested areas would be able to make informed decisions as to which plants will best succeed in their gardens," Simms said. "Knowing the host range will also help to narrow the import restrictions that are being placed on California plant and wood products by other states and countries."

The campus is responding in other ways, too:

* Signs are being posted to warn visitors that infectious spores may be present, and cautioning them not to remove plant material from the campus. Visitors also are urged to avoid muddy areas so as not to track spores to uninfected areas of the state or nation.

* The trunks and lower limbs of all oak trees in the known infected areas are being coated with a pesticide, copper sulphate, that Garbelotto found could prevent the microbe from entering the oak. Copper sulfate tree sprays are extensively used in organic orchards to treat fruit and nut crops for a wide variety of tree diseases.

* Copper sulphate treatment of trees will be minimized and limited to situations where they will have the highest likelihood of slowing or containing the infection. Yellow flags around trees indicate they have recently been treated with copper sulfate; they do not indicate that the trees are known to be infected.

* The campus is prepared to treat oaks, should any become infected, with a chemical fertilizer that has been shown to control pathogens related to the one that causes Sudden Oak Death. The chemical, phosphonate, would be injected into each infected tree just under the bark at the base of the trunk to attack the pathogen systemically. While research has not shown this can cure an infected tree, it may dramatically prolong the tree's life and slow the production of spores that spread the pathogen, Garbelotto said. The injections will be performed as part of a broad series of experiments on disease control and are not available to the public. He warns that the quality and efficacy of injection treatments sold by private firms cannot be guaranteed at this point.

"We're staying the course," said UC Berkeley's SOD Task Force leader Jim Horner, the campus landscape architect. "We are continuing to monitor and treat trees on campus."

Called Phytophthora ramorum (fi-TOFF-thoruh ra-MOR-um), the Sudden Oak Death pathogen is a member of the plant kingdom containing brown algae and a relative of the microbe responsible for the potato blight that launched a famine in Ireland 150 years ago. So far, it has been found to infect at least 14 and possibly more than 20 different plant species, though it apparently does not kill plants in all of those species.

Last November, after the disease was discovered at UC Berkeley, 172 plant samples were collected for analysis. Of the 102 plants samples analyzed to date, 34 or one-third contained DNA of Phytophthora ramorum. These included many bay laurels, a small number of tan oaks, sequoias and California buckeyes, but no oaks.

The wooded UC Berkeley campus is planted with some 300 species of trees, many dating from the 1870s and including between 800 and 1,000 coast live oaks.

The campus survey turned up potential new hosts, including the coast redwood, Sequoia sempervirens. The pathogen was found on dying shoots at the base of a redwood, but more tests must be done to determine if the pathogen killed the shoots and whether it affects mature trees.

"We still need to confirm that Phytophthora is a primary pathogen of redwood," said Garbelotto. "We have reason to believe redwoods are a potential host, and we are doing experiments to see if they are."

If the redwood proves to be a host, the disease could have a profound impact on the timber industry in California and the Pacific Northwest. It also would broaden the host range of the disease from hardwood flowering trees to the more economically important softwood conifers.

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